The present invention relates to a composition for film formation. More particularly, the invention relates to a composition for film formation which, when used as an interlayer insulating film material in the production of semiconductor devices and the like, can give silica-based films differing little in dielectric constant even when obtained through curing under different conditions and having excellent adhesion to substrates. The invention further relates to a process for producing the composition and a silica-based film.
Silica (SiO2) films formed by vacuum processes such as the CVD method have hitherto been used frequently as interlayer insulating films in semiconductor devices and other devices. In recent years, an insulating coating film which comprises a tetraalkoxysilane hydrolyzate as the main component and is called an SOG (spin on glass) film has come to be used for the purpose of forming a more even interlayer insulating film. Furthermore, as a result of the trend toward higher degree of integration in semiconductor devices and the like, an interlayer insulating film called an organic SOG film has been developed which comprises a polyorganosiloxane as the main component and has a low dielectric constant.
With further progress in the degree of integration or multilayer constitution especially in semiconductor devices and the like, better electrical insulation between conductors has come to be required and, hence, an interlayer insulating film material having a lower dielectric constant and excellent cracking resistance has come to be desired.
Proposed as materials having a low dielectric constant are a composition comprising a mixture of fine particles obtained by condensing an alkoxysilane in the presence of ammonia and a basic product of partial hydrolysis of an alkoxysilane (see JP-A-5-263045 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and JP-A-5-315319) and a coating fluid obtained by condensing a basic hydrolyzate of a polyalkoxysilane in the presence of ammonia (see JP-A-11-340219 and JP-A-11-340220). However, the materials obtained by these methods are unsuitable for industrial production because the reaction products have unstable properties and the films obtained therefrom have a large difference in dielectric constant depending on curing conditions and have considerable unevenness of properties such as adhesion to substrates.
An object of the invention is to provide a composition for film formation which eliminates the problems described above. More particularly, the object is to provide a composition for film formation which, when used in the production of semiconductor devices and the like, can give interlayer insulating films which differ little in dielectric constant even when obtained through curing under different conditions and have excellent adhesion to substrates. Another object of the invention is to provide a silica-based film obtained from the composition.
The invention provides a composition for film formation which comprises:
(A) a product of hydrolysis and condensation obtained by hydrolyzing and condensing
(A-1) at least one compound selected from the group consisting of compounds represented by the following formula (1) (hereinafter referred to as xe2x80x9ccompounds (1)xe2x80x9d)
RaSi(OR1)4xe2x88x92axe2x80x83xe2x80x83(1)
wherein R represents a hydrogen atom, a fluorine atom, or a monovalent organic group; R1 represents a monovalent organic group; and a is an integer of 1 or 2, compounds represented by the following formula (2) (hereinafter referred to as xe2x80x9ccompounds (2)xe2x80x9d)
Si(OR2)4xe2x80x83xe2x80x83(2)
wherein R2 represents a monovalent organic group, and compounds represented by the following formula (3) (hereinafter referred to as xe2x80x9ccompounds (3)xe2x80x9d)
R3b(R4O)3xe2x88x92bSixe2x80x94(R7)dxe2x80x94Si(OR5)3xe2x88x92cR6cxe2x80x83xe2x80x83(3)
wherein R3 to R6 may be the same or different and each represents a monovalent organic group; b and c may be the same or different and each is an integer of 0 to 2; R7 represents an oxygen atom, a phenylene group, or a group represented by xe2x80x94(CH2)nxe2x80x94, wherein n is an integer of 1 to 6; and d is 0 or 1, and
(A-2) at least one compound represented by the following formula (4) (hereinafter referred to as xe2x80x9ccompound (4)xe2x80x9d)
R83SiOR9xe2x80x83xe2x80x83(4)
wherein R8 and R9 each independently represents a monovalent organic group, in the presence of a catalyst and water; and
(B) an organic solvent.
The invention further provides a method of film formation which comprises applying the composition for film formation described above to a substrate and then heating the resulting coating.
The invention furthermore provides a silica-based film obtained by the method of film formation described above.